Passage 7.16.6
οὗτος μὲν δὴ ἀγαθὴν δόξαν Ἀθηναίοις καὶ αὑτῷ κτώμενος περιεποίησέ τε ὧν ἦρχε καὶ ἐτελεύτησεν αὐτὸς ἑκουσίως· Δίαιος δὲ Ἀχαιοὺς ἀπολωλεκὼς Μεγαλοπολίταις κακῶν τῶν ἐφεστηκότων ἧκεν ἄγγελος, ἀποκτείνας δὲ αὐτοχειρὶ τὴν γυναῖκα, ἵνα δὴ μὴ γένοιτο αἰχμάλωτος, τελευτᾷ πιὼν φάρμακον, ἐοικυῖαν μὲν παρασχόμενος Μεναλκίδᾳ τὴν ἐς χρήματα πλεονεξίαν, ἐοικυῖαν δὲ καὶ τὴν ἐς τὸν θάνατον δειλίαν.
This man, indeed, gained for the Athenians and himself a noble reputation, preserved those he governed, and willingly met his own end. Diaeus, however, after ruining the Achaeans, brought news to the Megalopolitans of the disasters that had befallen them; then, having slain his wife with his own hand to prevent her from becoming a captive, he ended his own life by drinking poison. He proved to resemble Menalcidas both in his greed for wealth and, similarly, in his cowardice regarding death.